In a biometric authentication system, biometric information, such as a fingerprint, a palm print, an iris, a retina, a blood vessel image, and a voice print, is used for authentication of a person. Such biometric information may be changed according to the season or the physical condition and aging of a person. When the biometric information is changed, there is a case where a person cannot be correctly authenticated in the biometric authentication system. For example, in the biometric authentication system using a fingerprint as biometric information, there is a case where it is difficult to perform fingerprint collation because, due to the physical condition of a person or the season, the state of the finger surface of the person at the time of collation is changed from the state of the finger surface of the person at the time of the registration.
In order to solve such problem, there have been proposed methods, such as a method (hereinafter referred to as a first conventional method) in which a registered image is selected on the basis of the quality of biometric images at the time of registration, and a method (hereinafter referred to as a second conventional method) in which registered data are replaced by using a biometric image inputted at the time of collation.